Surficial geochemistry, particularly selective leach technology, has proven effective in revealing anomalous concentrations of ore indicator metals overlying zones of buried mineralization. This study focuses on the buried Zn-Cu-Au-Ag VMS deposit at McIlvenna Bay in the Flin Flon Greenstone Belt to determine whether the peat swamp at the surface contains any anomalies of ore indicator metals using simple surficial geochemical techniques. Three selective leaches were performed, ammonium acetate pH 5.0, hydroxylamine, and sodium pyrophosphate. The hydroxylamine leach, which selects for metals in the reducible phase often associated with Mn and Fe oxides, has the clearest anomaly for multiple metals observed simultaneously, at the greatest magnitude. The pyrophosphate leach, which selects for metals that are oxidizable, often associated with organics showed a clear anomaly only for Cu, despite the abundance of organic matter and its great affinity for binding metals, likely because the organic-metal complexes formed in this system are easily exchangeable and highly soluble, not allowing for the formation of clear anomalies. The use of selective leach technology on surficial soil or peat has shown to be effective for delineating ore indicator metal anomalies, giving surface projections of buried mineralization in various types of systems, as long as the dynamics of the system are well understood in order to determine the phase the metals are associated with.

The basic fuel unit of the High Temperature Reactor (HTR) of the Pebble Bed Modular Reactor (PBMR) is a uranium dioxide kernel coated with a buffer layer, an inner pyrolytic carbon (IPyC) layer, a silicon carbide (SiC) layer and an outer pyrolytic carbon (OPyC) layer and is commonly referred to as a TRISO particle. Thousands of these micro-spheres are embedded in a graphite matrix and pressed to form a fuel sphere. During the manufacture of the TRISO particles and the fuel spheres there is a production of TRISO particles with cracked/broken layers, especially the SiC layer. Before the irradiation of the fresh fuel in the nuclear reactor it is of the utmost importance to quantify the failed fractions in fresh fuel as this information is very useful in the general understanding of fuel behaviour, calculation of risk and safety margins, and prediction of long term fuel behaviour. For this reason the burn-leach method has been applied for the quality control of the fresh fuel. In this work, several aspects of the burn-leach method that affect the efficiency of the method were studied. Aspects that were investigated are: qualitative aspects, layer properties, quantitative aspects, variants of the burn-leach method and lastly statistical information from the burn-leach data. The results obtained were as follows: Studies in this dissertation suggest that partial leaching of uranium in TRISO particles with a defective SiC layer was a phenomenon that exists. Although UO2 kernel equivalents were successfully determined by burn-leach method for particles with fully broken SiC layers, certain particles leached uranium amounts that did not correspond to single UO2 kernel equivalents; Evidence of occurrences of ‘slow leaching’ in an acidic medium were evident for certain particles. There were remnants of uranium dioxide kernels that had been partially leached after the full 16 hours. This behaviour led to inconclusive results on the absolute number of defective particles in a given population; Investigations suggest that there is at least circumstantial evidence that the BL method combined with X-ray tomography provides information about the integrity of the SiC layer, and why one particle leaches and the other does not. Neither the burn-leach nor the leach-burn-leach analysis is sufficient to be used as a stand-alone method to quantify the number of particles with defective SiC layers in a given TRISO particle population. The two tests need to be coupled to other techniques such as high resolution tomography for an extensive quantification of the layer defects; Burn-leach has to be designed to test for the layer integrity on a microscopic level as opposed to testing for the broken shells only, as was done by the normal burn-leach based on the German program. The leach time was not sufficient in its present form; Burn-leach results indicated that oxidation times of 96 hours at 750 °C under atmospheric pressure did not negatively affect the mechanical strength of the silicon carbide layer of freshly-manufactured TRISO particles, as these particles did not have a high failure fraction. / Dissertation (MSc)--University of Pretoria, 2013. / Materials Science and Metallurgical Engineering / Unrestricted

No description available.

Reducing the energy consumption of available resources is still a problem to be solved in Wireless Sensor Networks (WSNs). Many types of existing routing protocols are developed to save power consumption. In these protocols, cluster-based routing protocols are found to be more energy efficient. A cluster head is selected to aggregate the data received from root nodes and forwards these data to the base station in cluster-based routing. The selection of cluster heads should be efficient to save energy. In our proposed protocol, we use static clustering for the efficient selection of cluster heads. The proposed routing protocol works efficiently in large as well as small areas. For an optimal number of cluster head selection we divide a large sensor field into rectangular clusters. Then these rectangular clusters are further grouped into zones for efficient communication between cluster heads and a base station. We perform MATLAB simulations to observe the network stability, throughput, energy consumption, network lifetime and the number of cluster heads. Our proposed routing protocol outperforms in large areas in comparison with the LEACH, MH-LEACH, and SEP routing protocols.

The bulk of the world's known nickel reserves are contained in laterite ores but sulphidic ores remain the main source of the Western world's nickel production. With the continuing increase in nickel consumption and the depletion of sulphidic ores, the traditional source of nickel, the extraction of nickel from lateritic ores has been the subject of research interest worldwide. Advances in pressure acid leaching (PAL) technology have resulted in significant commercial attempts to extract nickel from these ores. Leaching the ore with sulphuric acid at elevated temperatures and pressures allows almost complete dissolution of the nickel and cobalt, a valuable byproduct of these ores, but yields highly contaminated pregnant leach solutions. Separating and purifying the nickel and cobalt from these solutions remains a hindrance to full commercial production. Several purifying techniques have been commercialised but all suffer from continuing technical problems. Among them, however, the direct solvent extraction (DSX) technique offers several advantages. Direct solvent extraction involves the separation of the nickel and cobalt directly from the partially neutralised pregnant liquor stream (PLS) by solvent extraction with Cyanex(R) 272 as the extractant. However certain contaminants adversely affect the solvent extraction process. Among them is chromium and little is known about the solvent extraction behaviour of this metal. The present work investigated the solvent extraction of chromium with Cyanex(R) 272. It was found that the solvent extraction behaviour of chromium(III) and chromium(VI), both of which could be found in PAL-generated PLS, are distinctly different. / For chromium(III), solvent extraction tests showed that (a) it is extracted in the pH range 4-7; (b) the extraction is partly influenced by diffusion; (c) the apparent equilibration time is significantly longer than most transition metals; (d) increases in temperature from 22 to 40 C resulted in increases in the extraction; (e) the pH0.5 increases in the order nitrate < chloride < sulphate in the presence of these anions; (f) the presence of acetate depresses extraction of chromium(III) when the solution is allowed to stand before extraction; (g) in the PLS, chromium(III) precipitated at lower pH than that predicted by the solubility product principle; and (h) the pH0.5 decreases as the Cyanex(R) 272 concentration increases. Chromium(III) is initially extracted by solvation of its inner sphere complex, which then undergoes further reaction in the organic phase leading to the formation of a much more stable species that is difficult to strip. A reaction scheme together with a description of both the initially extracted and resulting stable species is proposed. Extraction of chromium(VI), on the other hand, (a) occurs at pH less than 2 by solvation of chromic acid; (b) is independent of the aqueous phase composition; (c) does not occur in the pH range (3-6) used in the separation of nickel and cobalt. The latter is irrespective of temperature up to 40 C, the use of industrial PLS as the aqueous phase or the presence of an anti-oxidant in the organic phase. The stripping of chromium(III) from a loaded organic phase can be achieved using 1-4 mol L-1 mineral acids provided the stable organic species have not formed making industrial scale stripping of chromium(III) from Cyanex(R) 272 difficult. The exact composition of the aqueous phase during extraction affects the stripping efficiency.

In this study, evaluation of Kosovo-Artana Concentrator tailings with flotation and leaching method is aimed. The minerological analysis of sample showed that sphalerite, galena, chalcopyrite and their oxidised forms are the main ore minerals in the sample, while pyrite, illite, quartz, calcite and gypsum are the gangue minerals. The metal contents of the sample are 1.2% Zn, 0.75% Pb, and 0.06% Cu. Flotation tests to produce bulk concentrate of copper-lead and lead-zinc were unsatisfactory. The recovery of the zinc with H2SO4 leaching were conducted both at room temperature and at elevated temperature. The effects of various parameters such as leaching duration, concentration of H2SO4, pulp density and temperature on the zinc metal recovery were examined. The maximum extraction of zinc was 80% and 89% at room temperature and at 80 &deg / C respectively for 120 minutes leaching period.

The years between 1940 and 1964 constitute a significant period of growth of ceramics as part of the burgeoning Australian crafts movement. This phase is linked with Bernard Leach's influential text, A Potter's Book, where the author assesses the impact of this work on Australian ceramics. / The post-war years in Australia brought increased scope for leisure, work and education. Greater numbers of people than ever before became involved, as participants or audience, with activities in the cultural sphere. A notable feature of this time was a resurgence of interest in the manual arts. These traditional skills, reconfigured within contemporary society as creative hobbies or art related activities, became part of a movement known as the Crafts. / Nowhere was this more noticeable than with hand-made pottery in its transition from an essential trade to a redundant but nonetheless widely practiced craft and in the attendant social, aesthetic and theoretical shifts necessary to accommodate these changes in value, status and intent. Of all the activities coming within the ambit of the crafts, pottery garnered the most public interest. More people made pottery, more was written about pottery, more galleries exhibited pottery and more people bought pottery than any of the other crafts. Pottery was taught in almost every school and it often was the only hand-craft taught at a tertiary level. In examining the transformation of Australian ceramics during this time one can isolate many factors that played a part, but underpinning much of this activity was a remarkably influential book, Bernard Leach’s 1940 publication ‘A Potter’s Book’. / Building on a legacy of cross-cultural borrowings, Leach may be credited with establishing Japan as the site of craft authenticity in the imagination of countless potters. Added to this is the significance of ‘A Potter’s Book’ as an invaluable technical aid, at a time when there was little practical information specifically tailored to the needs of the studio potter. / The years between 1940 and 1964 constitute a significant period in the growth of ceramics as part of the burgeoning Australian Crafts Movement. By concentrating on this crucial phase of Australian pottery and linking it to what was the most influential text in the field, a framework is created to assess the depth and variety of practice. / Looking at Australian Pottery through the structures and arguments set forth in ‘A Potter’s Book’, an assessment of the impact of this important work on Australian ceramics can be made that extends beyond the anecdotal. Despite the importance of Leach’s text and the unprecedented vitality of Australian pottery at the time, no significant analysis of the degree of connectivity between the two exists. This thesis hopes to contribute to a fuller understanding of this area of Australian craft history. / Thesis (PhD)--University of South Australia, 2006.

A biologia reprodutiva de machos e fêmeas de Artibeus lituratus e Artibeus fimbriatus foi estudada no extremo sul do Brasil, região subtropical e limite meridional de suas distribuições. O padrão reprodutivo dessas espécies é conhecido somente nas zonas tropicas do Brasil. Para as análises foi utilizado um total de 225 indivíduos de A. lituratus (86 machos e 139 fêmea) e 129 indivíduos de A. fimbriatus (46 machos e 83 fêmeas), depositados em coleções científicas, coletados no estado de Rio Grande do Sul e sudeste Sul de Santa Catarina. O ciclo reprodutivo foi estudado a partir da análise de caracteres sexuais externos e análise de lâminas histológicas das gônadas de machos e fêmeas. Somente indivíduos adultos foram considerados para as análises. As fêmeas de A. lituratus e A. fimbriatus apresentam dois períodos reprodutivos ao ano, padrão reprodutivo poliéstrico bimodal, e os machos permanecem ativos ao longo de todo o ano. O tempo de gestação dura, aproximadamente, de três a quatro meses. Os períodos de nascimento ocorrem entre novembro e fevereiro, enquanto que os de amamentação vão de fevereiro a maio, épocas correspondentes à primavera e verão, quando as temperaturas são mais elevadas e os dias mais longos no extremo sul do Brasil.

A biologia reprodutiva de machos e fêmeas de Artibeus lituratus e Artibeus fimbriatus foi estudada no extremo sul do Brasil, região subtropical e limite meridional de suas distribuições. O padrão reprodutivo dessas espécies é conhecido somente nas zonas tropicas do Brasil. Para as análises foi utilizado um total de 225 indivíduos de A. lituratus (86 machos e 139 fêmea) e 129 indivíduos de A. fimbriatus (46 machos e 83 fêmeas), depositados em coleções científicas, coletados no estado de Rio Grande do Sul e sudeste Sul de Santa Catarina. O ciclo reprodutivo foi estudado a partir da análise de caracteres sexuais externos e análise de lâminas histológicas das gônadas de machos e fêmeas. Somente indivíduos adultos foram considerados para as análises. As fêmeas de A. lituratus e A. fimbriatus apresentam dois períodos reprodutivos ao ano, padrão reprodutivo poliéstrico bimodal, e os machos permanecem ativos ao longo de todo o ano. O tempo de gestação dura, aproximadamente, de três a quatro meses. Os períodos de nascimento ocorrem entre novembro e fevereiro, enquanto que os de amamentação vão de fevereiro a maio, épocas correspondentes à primavera e verão, quando as temperaturas são mais elevadas e os dias mais longos no extremo sul do Brasil.

A biologia reprodutiva de machos e fêmeas de Artibeus lituratus e Artibeus fimbriatus foi estudada no extremo sul do Brasil, região subtropical e limite meridional de suas distribuições. O padrão reprodutivo dessas espécies é conhecido somente nas zonas tropicas do Brasil. Para as análises foi utilizado um total de 225 indivíduos de A. lituratus (86 machos e 139 fêmea) e 129 indivíduos de A. fimbriatus (46 machos e 83 fêmeas), depositados em coleções científicas, coletados no estado de Rio Grande do Sul e sudeste Sul de Santa Catarina. O ciclo reprodutivo foi estudado a partir da análise de caracteres sexuais externos e análise de lâminas histológicas das gônadas de machos e fêmeas. Somente indivíduos adultos foram considerados para as análises. As fêmeas de A. lituratus e A. fimbriatus apresentam dois períodos reprodutivos ao ano, padrão reprodutivo poliéstrico bimodal, e os machos permanecem ativos ao longo de todo o ano. O tempo de gestação dura, aproximadamente, de três a quatro meses. Os períodos de nascimento ocorrem entre novembro e fevereiro, enquanto que os de amamentação vão de fevereiro a maio, épocas correspondentes à primavera e verão, quando as temperaturas são mais elevadas e os dias mais longos no extremo sul do Brasil.